I took a step back today and decided to unshroud the valves.
This caused me to have to polish out the chamber sides again but
it wasn’t too much additional work. This will help flow, and also
give me slightly more chamber volume as well.
You can see the various stages of chamber finish.
Today I CC’d the finished chambers to measure for uniformity,
as well as compare against a stock STI head so that the
static compression ratio could be calculated.
The measured size of my chambers was 52cc and the
measured size of the STI chamber was 57cc. The STI
compression ratio should be 8.2:1 using a stock piston.
My compression ratio should be 8.7:1 and I feel that’s
easily within the desired range of what I have planned for this engine.
Tonight I jumped back to the bottom end to wrap up the short block
and get it mounted on a stand. Indexed the rings, after
measuring them, there was only about ½ thou difference in
ring gap so no need to gap them. Next the pistons,
wristpins and locks were installed. Then, the plugs, covers,
and rear main seal were installed.
The holes thru the center of the TGV’s, were tapped and plugged.
I installed stock valves and measured them for height,
so there would be a point of reference. Once I had
the measurements, I started the process of shortening
the STI valves to the same installed height.
As a side note I quickly weighed the stock wrx and hollow sti
valves to see what kinda weight difference there is.
As you can see its minimal but every little bit helps!
Next I installed new valve seals,and began to assemble the heads.
Valves go in first being sure to lube the ends where they have to slide thru new valve
seals. We have some 09 WRX valve springs, some titanium retainers,
and stock Subaru spring seats and locks.
Cylinder head assembly is pretty straight forward but we took some pictures anyway!